The most common application of insert molding is brass insert molding. It is a mature plastic molding technology. Put the brass insert into the mold to inject with the plastic to form a single part manually or mechanically. The main function is to make use of the machined screws instead of self-tapping ones, thus make the product can be assembled and disassembled time and again. There are many different types brass inserts in the market, some of them is customized for a certain situation. Anyway, the main objective is to ensure the strength of the combination.
Another application is to insert a part of metal to meet with the high precision requirements (typically plastic parts has an at least ±0.1mm tolerance) or realize the function of electricity conduction, sometimes because of the looks.
BDM provide you the mature whatever hard (ABS, PC etc.) or soft plastic insert molding (TPE,TPU) technique.